Efficacy of Lipid Apheresis: Definitions and Influencing Factors

The comparison of efficiency of currently available lipid apheresis systems has been hampered by different definitions of efficacy and poorly controlled apheresis conditions. This paper suggests definitions of efficacy and standardization of its determinants. The acute efficacy of risk factor reduction reflects the relative decrease of pathogen by a single treatment session compared to preapheresis levels. Standardization of treated plasma volume in relation to the patients plasma volume and correction of changes in plasma volume during the procedure are mandatory. Its determination is most useful in the technical evaluation of new systems. The long-term efficacy of risk factor reduction as compared to baseline is determined by mean interapheresis levels of e.g. LDL-C in the pseudo-steady-state after about 3 months of regular treatment. It is the major criterion for potential regression of coronary artery disease and absolute average plasma levels of 120 ≤ mg/dl LDL-C should be attained. It is influenced by the acute efficacy of the system, apheresis frequency and rebound kinetics. The clinical efficacy is defined by apheresis induced reduction of coronary morbidity and mortality. It is influenced by long-term risk factor reduction, the selectivity of the system as well as the control of non-lipid risk factors. Apheresis related effects on coronary artery disease comprise functional improvements of hemorheology and vasomotion as well as morphological benefits like regression of luminal narrowing and plaque stabilization. In conclusion, the acute efficacy of apheresis systems should be determined under strictly controlled conditions; however, as apheresis independent factors influence long-term efficacy and, even more so, clinical efficacy of the treatment, differences between the available systems are blurred so that factors like costs and ease of handling may eventually significantly influence the choice of procedure.

Hyperhomocysteinemia, hyperfibrinogenemia, and lipoprotein (a) excess in maintenance dialysis patients: a matched case-control study

Maintenance dialysis patients experience an exceedingly high incidence of arteriosclerotic cardiovascular disease (CVD) events that are poorly predicted by traditional CVD risk factor indices. We evaluated the prevalence of three non-traditional CVD risk factors, i.e. hyperhomocysteinemia, hyperfibrinogenemia, and lipoprotein (a) Lp(a)) excess, and combined hyperhomocysteinemia, hyperfibrinogenemia, and Lp(a) excess, in maintenance dialysis patients. Fasting total plasma homocysteine (Hcy), fibrinogen, Lp(a), glucose, and total and HDL cholesterol levels, and traditional CVD risk factor (i.e. glucose tolerance, smoking, hypertension, dyslipidemia) prevalences were assessed in 71 dialysis patients and 71 age, sex, and race matched Framingham Study controls free of clinical renal disease, with normal serum creatinine (< or = 1.5 mg/dl). Mean plasma Hcy 23.7 vs. 9.9 microM, P = 0.0001), fibrinogen (457 vs. 309 mg/dl, P = 0.0001), and Lp(a) (30 vs. 17 mg/dl, P = 0.0070) levels were substantially increased in the dialysis patients. Matched odds ratios (with 95% confidence intervals), dialysis patients/controls, for hyperhomocysteinemia, hyperfibrinogenemia, and Lp(a) excess, alone or combined, were markedly greater in the dialysis patients, with no evidence of confounding by the traditional CVD risk factors: hyperhomocysteinemia, 105.0 (29.9-368.9); hyperfibrinogenemia, 16.6 (6.6-42.0); Lp(a) excess, 3.5 (1.5-8.4); all three combined 35.0 (5.7-199.8). Given in vitro evidence that Hcy, Lp(a), and fibrinogen interact to promote atherothrombosis, combined hyperhomocysteinemia, hyperfibrinogenemia, and Lp(a) excess may contribute to the high incidence of vascular disease sequelae experienced by dialysis patients, which is inadequately explained by traditional CVD risk factors. Controlled, prospective studies of well-characterized maintenance dialysis cohorts are urgently required to substantiate this hypothesis.

Lipid apheresis: from a heroic treatment to routine clinical practice

Lipid apheresis has developed from a heroic treatment into a routine clinical therapy and currently is the major indication for performing extracorporeal plasma therapy. Whereas it was once reserved for patients with homozygous familial hypercholesterolemia, today it has a place in the secondary prevention of severe coronary heart disease when low-density lipoprotein (LDL)-cholesterol level exceeds 150 mg/dl, despite conservative treatment, in any type of primary hypercholesterolemia. Unselective plasma exchange has been replaced by a variety of selective procedures. The efficacy of the treatment can be maximized by combining LDL apheresis with the use of cholesterol synthesis enzyme inhibitors. Clinical studies have shown that drastic cholesterol reduction can result in regression of coronary atherosclerosis as well as in reduced cardiac morbidity and mortality. Technical progress comprises improved selectivity, online regeneration of adsorbers, and LDL adsorption from whole blood. Recently, a new LDL hemoperfusion procedure was successfully tested in a clinical pilot study; blood is passed directly over a lipid sorbent without prior plasma separation. If this system is demonstrated to be safe and effective in clinical Phase III trials, a further qualitative step in the rapid development of LDL apheresis will have made.